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 these ancient events shaped the topography in a broad way, its final development was comparatively recent, during the glacial period, when the loose materials were scoured from some regions and spread out as boulder clay, or piled up as moraines in others; and the original water-ways were blocked in many places. The retreat of the ice left Canada much in its present condition except for certain post-glacial changes of level which seem to be still in progress. For this reason the region has a very youthful topography with innumerable lakes and waterfalls as evidence that the rivers have not long been at work. The uneven carving down of the older mountain systems, especially that of the Archean pro taxis, and the disorderly scattering of glacial material provide most of the lake basins so characteristic of Canada.

Lakes and Rivers.—As a result of the geological causes just mentioned many parts of Canada are lavishly strewn with lakes of all sizes and shapes, from bodies of water hundreds of miles long and a thousand feet deep to ponds lost to sight in the forest. Thousands of these lakes have been mapped more or less carefully, and every new survey brings to light small lakes hitherto unknown to the white man. For numbers they can be compared only with those of Finland and Scandinavia in Europe, and for size with those of eastern Africa; but for the great extent of lake-filled country there is no comparison. From the map it will be noticed that the largest and most thickly strewn lakes occur within five hundred or a thousand miles of Hudson Bay, and belong to the Archean protaxis or project beyond its edges into the Palaeozoic sedimentary rocks which lean against it. The most famous of the lakes are those of the St Lawrence system, which form part of the southern boundary of Canada and are shared with the United States; but many others have the right to be called “Great Lakes” from their magnitude. There are nine others which have a length of more than 100 m., and thirty-five which are more than 50 m. long. Within the Archean protaxis they are of the most varied shapes, since they represent merely portions of the irregular surface inundated by some morainic dam at the lowest point. Comparatively few have simple outlines and an unbroken surface of water, the great majority running into long irregular bays and containing many islands, sometimes even thousands in number, as in Georgian Bay and Lake-of-the-Woods. In the Cordilleran region on the other hand the lakes are long, narrow and deep, in reality sections of mountain valleys occupied by fresh water, just as the fjords of the adjoining coast are valleys occupied by the sea. The lakes of the different regions present the same features as the nearest sea coasts but on a smaller scale. The majority of the lakes have rocky shores and islands and great variety of depth, many of the smaller ones, however, are rimmed with marshes and are slowly filling up with vegetable matter, ultimately becoming peat bogs, the muskegs of the Indian. Most of Canada is so well watered that the lakes have outlets and are kept fresh, but there are a few small lakes in southern Saskatchewan, e.g. the Quill and Old Wives lakes, in regions arid enough to require no outlets. In such cases the waters are alkaline, and contain various salts in solution which are deposited as a white rim round the basin towards the end of the summer when the amount of water has been greatly reduced by evaporation. It is interesting to find maritime plants, such as the samphire, growing on their shores a thousand miles from the sea and more than a thousand feet above it. In many cases the lakes of Canada simply spill over at the lowest point from one basin into the next below, making chains of lakes with no long or well-defined channels between, since in so young a country there has not yet been time for the rivers to have carved wide valleys. Thus canoe navigation may be carried on for hundreds of miles, with here and there a waterfall or a rapid requiring a portage of a few hundred yards or at most a mile or two. The river systems are therefore in many cases complex and tortuous, and very often the successive connecting links between the lakes receive different names. The best example of this is the familiar one of the St Lawrence, which may be said to begin as Nipigon river and to take the names St Mary’s, St Clair, Detroit and Niagara, before finally flowing from Lake Ontario to the sea under its proper name. As these lakes are great reservoirs and settling basins, the rivers which empty them are unusually steady in level and contain beautifully clear water. The St Lawrence varies only a few feet in the year and always has pellucid bluish-green water, while the Mississippi, whose tributaries begin only a short distance south of the Great Lakes, varies 40 ft. or more between high- and low-water and is loaded with mud. The St Lawrence is far the most important Canadian river from the historic and economic points of view, since it provided the main artery of exploration in early days, and with its canals past rapids and between lakes still serves as a great highway of trade between the interior of the continent and the seaports of Montreal and Quebec. It is probable that politically Canada would have followed the course of the States to the south but for the planting of a French colony with widely extended trading posts along the easily ascended channel of the St Lawrence and the Great Lakes, so that this river was the ultimate bond of union between Canada and the empire.

North of the divide between the St Lawrence system and Hudson Bay there are many large rivers converging on that inland sea, such as Whale river, Big river, East Main, Rupert and Nottaway rivers coming in from Ungava and northern Quebec; Moose and Albany rivers with important tributaries from northern Ontario; and Severn, Nelson and Churchill rivers from the south-west. All of these are rapid and shallow, affording navigation only for canoes; but the largest of them, Nelson river, drains the great Manitoban lakes, Winnipeg, Winnipegosis and Manitoba, which are frequented by steamers, and receive the waters of Lake-of-the-Woods, Lake Seul and many others emptying into Winnipeg river from Ontario; of Red river coming in from the United States to the south; and of the southern parts of the Rocky Mountains and the western prairie provinces drained by the great Saskatchewan river. The parallel of 49° approximately separates the Saskatchewan waters from the streams going south to the Missouri, though a few small tributaries of the latter river begin on Canadian territory.

The northern part of Alberta and Saskatchewan and much of northern British Columbia are drained through the Athabasca and Peace rivers, first north-eastwards towards Athabasca Lake, then north through Slave river to Great Slave Lake, and finally north-west through Mackenzie river to the Arctic Ocean. If measured to the head of Peace river the Mackenzie has a length of more than 2000 m., and it provides more than 1000 m. of navigation for stern-wheel steamers. Unfortunately, like other northward-flowing rivers, it does not lead down to a frequented sea, and so bears little traffic except for the northern fur-trading posts. The Mackenzie forms a large but little-known delta in lat. 69°, and in its flood season the head-waters pour down their torrents before the thick ice of the lower part with its severer climate has yet given way, piling up the ice in great barriers and giving rise to widespread floods along the lower reaches. Similar flooding takes place in several other important northward-flowing rivers in Canada, the St Lawrence at Montreal affording the best-known instance. Second among the great north-western rivers is the Yukon, which begins its course about 18 m. from tide-water on an arm of the Pacific, 2800 ft. above the sea and just within the Canadian border. It flows first to the north, then to the north-west, passing out of the Yukon territory into Alaska, and then south-west, ending in Bering Sea, the northward projection of the Pacific, 2000 m. from its head-waters. Of its course 1800 m. are continuously navigable for suitable steamers, so that most of the traffic connected with the rich Klondike gold-fields passes over its waters. The rest of the rivers flowing into the Pacific pass through British Columbia and are much shorter, though the two southern ones carry a great volume of water owing to the heavy precipitation of snow and rain in the Cordilleran region. The Columbia is the largest, but after flowing north-west and then south for about 400 m., it passes into the United States. With its expansions, the narrow and deep Arrow lakes, it is an important waterway in the Kootenay region. The Fraser, next in size but farther north, follows a similar course, entering the sea at Vancouver; while the Skeena and Stikine in northern British Columbia are much